In fabrication of electronic devices such as semiconductor devices, many efforts have been focused on integrating more patterns in a limited area of a semiconductor substrate. That is, attempts to increase the integration density of electronic devices such as semiconductor devices have typically focused on formation of fine patterns. Various techniques have been proposed to form fine patterns, such as small contact holes having a nano-scale critical dimension (CD) with a size of about a few nanometers to about several tens of nanometers. In the event that the fine patterns of the semiconductor devices are formed using only a photolithography process, there may be some limitations in forming the fine patterns due to image resolution limits of lithography apparatuses used in the photolithography process.
Methods of forming fine patterns using self-assembly of polymer molecules may be considered as a candidate for overcoming the image resolution limits of optical systems used in the photolithography process and for overcoming wavelengths of lights generated from light sources of optical systems used in the photolithography process. However, methods of forming fine patterns using self-assembly techniques are in development. Thus, there are still some difficulties in forming the fine patterns of highly integrated semiconductor devices using self-assembly techniques.